Install for Hugs.
For install, copy-prefix = prefix, but for copy they're different.
The library goes in <copy-prefix>/lib/hugs/packages/<pkgname>
(i.e. <prefix>/lib/hugs/packages/<pkgname> on the target system).
Each executable goes in <copy-prefix>/lib/hugs/programs/<exename>
(i.e. <prefix>/lib/hugs/programs/<exename> on the target system)
with a script <copy-prefix>/bin/<exename> pointing at
<prefix>/lib/hugs/programs/<exename>.